International weather agencies object to 5G spectrum decision

The Advanced Technology Microwave Sounder, a key instrument on the first satellite in the National Oceanic and Atmospheric Administration (NOAA) Joint Polar Satellite System, observes microwave radiation emitted by Earth’s surface and atmosphere. The satellite pictured, NOAA-20, was declared operational in May 2018. Credit: NOAA

SAN FRANCISCO – A decision made at the recent World Radiocommunication Conference could undermine the accuracy of weather forecasts by interfering with meteorological satellite observations, according to the World Meteorological Organization (WMO) and the European Center for Medium-Range Weather Forecasts (ECMWF).

“The race to release 5G technology threatens to squeeze out other radio-frequency dependent technologies, including the world’s critical national severe weather early warning systems,” the WMO said in Nov. 27 news release.

Delegates to the International Telecommunications Union’s World Radiocommunication Conference 2019, which concluded Nov. 22 in Egypt, agreed to allow 5G technologies to operate in four areas of the radio frequency spectrum including a band from 24.25 to 27.5 GHz. Meteorologists are concerned transmissions in that band could interfere with the ability of passive microwave sensors on weather satellites to detect atmospheric water vapor by observing faint signals emitted from 23.6 to 24 GHz.

In an effort to prevent 5G transmissions from interfering with weather observations, World Radiocommunications Conference delegates adopted a rule requiring 5G equipment operating from 24.25-27.5 GHz to limit the strength of signals spilling over into the 24 gigahertz frequency to -33 decibel watts.

The WMO and ECMWF said that the limit is not stringent enough. The WMO said the new rules “could lead to nearly ten times more interfering out-of-band emissions than” limits the WMO recommended. Prior to the World Radiocommunications Conference, the WMO called for 5G base stations to limit noise in adjacent bands to -55 decibel watts and -51 decibel watts for 5G user equipment.

International negotiators in Egypt agreed to phase in more stringent limits based on the idea that 5G equipment will not interfere with microwave sensors until the equipment is distributed widely. As a result, the negotiators agreed to adopt limits of -39 decibel watts for 5G base stations and -35 decibel watts for mobile equipment fielded after Sept. 1, 2027.

“The risk, therefore, is that 5G could roll-out more quickly than initially anticipated, creating an unregulated increase in interference in the 24 GHz” spectrum band, according to the WMO news release.

Renee A. Leduc, founder of Narayan Strategy, a Washington-based weather and climate policy consulting firm, said the deal “incentivizes wireless companies to be even more aggressive in deploying 5G before 2027.” Under the terms of the deal reached in Egypt, wireless companies will not be required to replace technology they deploy prior to 2027 as soon as the new rules go into effect. Instead, they will need to ensure equipment fielded after 2027 complies with the more stringent standards, Clarke added.

WMO Secretary-General Petteri Taalas said in a statement, “This WRC-19 decision has the potential to significantly degrade the accuracy of data collected in this [24 GHz] frequency band, which would jeopardize the operation of existing Earth observation satellite systems essential for all weather forecasting and warning activities of the national weather services. Potential effects of this could be felt across multiple impact areas including aviation, shipping, agricultural meteorology and warning of extreme events as well as our common ability to monitor climate change in the future.”

“We have worked closely with the community to explain and highlight the risks attached to 5G operators being allowed to transmit at close proximity to meteorological frequencies,” ECMWF said in a Nov. 25 statement. “The agreement reached in Egypt falls far short of ensuring 5G applications do not interfere with weather observations at 24 GHz.”